MathNet 2016-part-03 — 184 problems (EN–VI) Question 137

Compute:

a) $I_{1} = \int (\cos x \cdot \cos 2x \cdot \cos 3x) \, dx$

b) $I_{2} = \int_{1}^{\sqrt{3}} \frac{1}{x \sqrt{x^{4} + 1}} \, dx$